Man's Place in the Universe: A Study of the Results of Scientific Research in Relation to the Unity or Plurality of Worlds, 3rd EditionWallace, Alfred Russel
Science
Man's Place in the Universe: A Study of the Results of Scientific Research in Relation to the Unity or Plurality of Worlds, 3rd Edition
Wallace, Alfred Russel
Life; Plurality of worlds; Stars
Now it is found that from the first to the sixth magnitude the stars
increase in number at the rate of about three and a half times those of the
preceding magnitudes. The total number of stars down to the sixth magnitude
is given by Professor Newcomb as 7647. For higher magnitudes the numbers
are so great that precision and uniformity are more difficult of
attainment; yet there is a wonderful continuance of the same law of
increase down to the tenth magnitude, which is estimated to include
2,311,000 stars, thus conforming very nearly with the ratio of 3.5 as
determined by the lucid stars.
But when we pass beyond the tenth magnitude to those vast numbers of faint
stars only to be seen in the best or the largest telescopes, there appears
to be a sudden change in the ratio of increased numbers per magnitude. The
numbers of these stars are so great that it is impossible to count the
whole as with the higher magnitude stars, but numerous counts have been
made by many astronomers in small measured areas in different parts of the
heavens, so that a fair average has been obtained, and it is possible to
make a near approximation to the total number visible down to the
seventeenth magnitude. The estimate of these by astronomers who have made a
special study of this subject is, that the total number of visible stars
does not exceed one hundred millions.[3]
But if we take the number of stars down to the ninth magnitude, which are
known with considerable accuracy, and find the numbers in each succeeding
magnitude down to the seventeenth, according to the same ratio of increase
which has been found to correspond very nearly in the case of the higher
magnitudes, Mr. J.E. Gore finds that the total number should be about 1400
millions. Of course neither of these estimates makes any pretence to exact
accuracy, but they are founded on all the facts at present available, and
are generally accepted by astronomers as being the nearest approach that
can be made to the true numbers. The discrepancy is, however, so enormous
that probably no careful observer of the heavens with very large telescopes
doubts that there is a very real and very rapid diminution in the numbers
of the fainter as compared with the brighter stars.
There is, however, yet one more indication of the decreasing numbers of the
faint telescopic stars, which is almost conclusive on this question, and,
so far as I am aware, has not yet been used in this relation. I will
therefore briefly state it.
THE LIGHT RATIO AS INDICATING THE NUMBER OF FAINT STARS
Professor Newcomb points out a remarkable result depending on the fact
that, while the average light of successively lower magnitudes diminishes
in a ratio of 2.5, their numbers increase at nearly a ratio of 3.5. From
this it follows that, so long as this law of increase continues, the total
of starlight goes on increasing by about forty per cent. for each
successive magnitude, and he gives the following table to illustrate it:--
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